Ob INSECTICIDES, FUNGICIDES, AND WEED KILLERS. 



sensitiveness to this reagent, and it has been observed, for example, that 

 trees generally support larger doses than annual plants. The aerial 

 part of the plant also withstands carbon disulphide up to a certain 

 limit, soapy emulsions and fumigations of carbon disulphide which, 

 according to Morren, are not toxic up to j-^jj-fj- Goethe has observed 

 that the vine can stand fumigations for twelve hours at 20° C. without 

 suffering. Before the ascent of the sap the vapours of carbon 

 disulphide may be prolonged without injury, and the dose in the same 

 way. Targioni-Tozetti found that the dose of 2 per cent of carbon 

 disulphide in soapy emulsion was the limit without injury to the leaves, 

 whilst with petrol the dose was 2*5 per cent. A sti'ong dose of carbon 

 disulphide dries the leaves without altering the colour. Seeds like- 

 wise undergo the toxic effect of this insecticide, but according to 

 Prillieux their power to withstand it varies with the species. Cereals, 

 for example, lose 50 per cent of their germinative capacity after eight 

 days of fumigation, whilst beet seeds undergo no alteration after three 

 weeks of this same treatment. Coupin, who examined the action of 

 this agent on grain compared with ether and chloroform, found that 

 these two last bodies had no injurious action on wheat grain when 

 the protoplasm is at I'est, whilst carbon disulphide is alw^ays in- 

 jurious thereto. Howevei-, if owing to moisture there is swelling 

 and the protoplasm is active, ether also becomes injurious to the 

 grain in the dose of 3-7 c.c. for 10 litres of air (3-7 in 10,000). 

 According to Fantecchi's experiments seed corn dipped two minutes 

 in carbon disulphide and afterwards dried in the air loses 10 per cent ; 

 dipped for one minute only in this insecticide then exposed after- 

 wards for twenty-four hours in an atmosphere of carbon disulphide, 

 it undergoes a loss of 50 per cent. The grain suffers the same loss 

 if exposed for twenty-four hours in a closed vessel at 30° C. (86° F.) ; 

 in an atmosphere containing 2 kilogrammes of carbon disulphide per 

 cubic metre if the heat be raised to 40° C. (104° F.) the loss will be 

 100 per cent. 



Action of Carbon Disulphide on Insects. — Carbon disulphide 

 is one of the most efficacious of insecticides ; it diffuses very rapidly in 

 virtue of its great mobility and its very low boiling-point. Its 

 aucesthetic and asphyxiant j)roperties act very rapidly on the vitality 

 of the insects w^hich die paralysed in breathing it. Insects are gener- 

 ally more sensitive to the action of carbon disulphide than plants, so 

 that by only using doses injurious to insects they can be overcome 

 without hurting the plant. When an atmosphere saturated with the 

 vapour of carbon disulphide can be created around the insects or 

 their larvae they die in a few seconds (Mouillefert). Phylloxera is so 

 killed in thirty seconds. If the atmosphere only contains 0'5 per 

 cent of carbon disulphide vapours (say 0-0016 of liquid sulphide) the 

 action must last twenty-four hours to kill the phylloxera. An 

 atmosphere containing 0-4 per cent of CS.^ vapour easily kills, in 

 fifteen minutes, grubs, butterflies, grasshoppers, lice, and Coleoptera 

 (balls) . Injected into the soil to a depth of 4 inches doses of 40 grammes 

 per square metre (say 1^ oz. per square yard) for heavy ground and 

 30 gramoies (say 1 oz. per square yard) for dry, light soil, suffices 



